The invention relates to a driver assistance system for a motor vehicle having a controller for the regulation of the acceleration of the motor vehicle according to a setpoint acceleration.
In general, driver assistance systems for longitudinal guidance of a vehicle can be implemented for a number of different spheres of action. Thus, for example, informational and/or warning distance-information systems indicate in an acoustical, optical or haptical manner to the driver that the distance of the motor vehicle from a preceding vehicle is too short. Then, the driver can decide whether and how he can correct, as a function of the situation, his driving speed and the momentary distance. Assistance systems, which make semi-automatic recommendations, use, for example, a so-called active gas pedal, which immediately informs the driver about the momentary “correct” gas pedal position by means of artificial additional forces in the gas pedal. The gas pedal position is necessary for maintaining the adapted speed or the correct distance from a preceding vehicle. The driver himself decides how he wants to translate the information regarding the correcting value that is proposed directly by the system. Automatic distance control systems, such as an ACC system, endeavor to assume the entire longitudinal guidance for specific driving situations.
The driving speed control system or the ACC system usually enables the driver to set the desired speed at the steering wheel using an operator control element, for example a pitman arm or push buttons. Then, the system controls the speed, if desired, as a function of the temporal distance from a vehicle traveling ahead.
Then, the driver can change the desired speed with the pitman arm and/or the push buttons, or can deactivate the system with these operator control elements. Furthermore, it is usually possible for the driver to override (equals higher speed) the system by using the gas pedal. As a result, the control system ceases temporarily to have an effect; and the system is deactivated with the brake pedal. According to this prior art system philosophy, the driver can either rely on the system and let the system drive, in which case certain specifications can be made, as described above; or the driver can turn off the system and do the driving himself. If the driver lets the system drive, he becomes an observer/monitor of the system and can indirectly influence the system, but he is not actively involved in the control process (maintaining speed and distance). When the system reaches one of its limits, the step demands that the driver assumes the active control again—a role change. Many drivers find this role change to be inconvenient and, hence, it is delayed as long as possible.
According to the current and foreseeable future of the state of the art that can be expected, it is not possible to transfer the entire longitudinal guidance of the vehicle to the driver assistance system. There are still a number of driving situations, with which the automatic distance control system cannot cope or can cope only to an inadequate extent in practical traveling situations. Important factors are, on the one hand, the limited detection capacity of the conventional modern driving environment sensing systems. However, on the other hand, the decisive factor is of a generic nature. From the perspective of the overall task of driving, the ACC fully automates to some degree individual tasks within the total longitudinal guidance task, which interferes to a considerable extent with the remaining operating and control activities of the driver. The driver must interact with the automatic system. In the case of ACC, this system is programmed in essence only with respect to maintaining the distance or—during unobstructed travel—with respect to maintaining a desired speed. However, driving a car is a dynamic process, during which it is usually not possible to maintain absolutely constant time gaps or fixed desired speeds, but rather deviations from these simple rules of the ACC system occur at a significant frequency. As a result, a plethora of conflicts with the driver's expectations or a typical behavior of the driver are preprogrammed.
Some examples are vehicles cutting in front of the vehicle, vehicles turning off, sensor coverage ranges that are too short, late reaction to a fast approaching vehicle, imprecise/uncertain lane allocation, lane change, limited deceleration capacity, no reaction to objects that are standing still, misinterpretation of apparently relevant objects, non-detection of relevant objects, etc.
In these cases, as stated above, the driver has the choice in the modern functional and operating designs of the ACC of either turning off the system or taking over the control himself by depressing the OFF button. Or, if some other deceleration than that initiated by the system is necessary, the driver can turn it off at the same time that he operates the brake pedal. In order to generate an acceleration that is higher than that specified by the system, the driver has to operate the gas pedal. In this case, the system function recedes briefly into the background and is re-activated when the gas pedal is released. In both cases, an interruption in the natural dynamic flow of travel is produced with the disengagement. Re-engagement, which often follows a short time after the disengagement, usually brings about a clearly perceptible transient effect. Furthermore, in both cases the intervention also involves an excessive manual operating effort.
In order to achieve better acceptance and a more harmonic interaction between the driver and the semi-automated system, it is, therefore, advised to provide measures that enable better involvement of the driver in order to improve the method for informing the system, on the one hand, of the driver's diverging assessment of the driving situation and, on the other hand, in particular, his intentions, so that the entire driving process is more homogeneous.
To this end, German patent document DE 103 03 611 A1 describes a speed controller with a plurality of operating modes, where a “stop and go mode” is provided as one operating mode; and an ACC mode is provided as a second operating mode. In these two modes, it is possible for the driver to operate the gas pedal and, thus, override the stop and go control function and/or the ACC control function. Therefore, during override, these functions are deactivated and are resumed following the override.
Furthermore, German patent document DE 10 2004 040 532 A1 discloses a vehicle object detection system, a preceding vehicle following control system, and a vehicle control system, which exhibits an acceleration/deceleration request detector for sensing an occupant's request for an acceleration or deceleration on the basis of the actuation of the brake pedal by the occupant, the actuation of a gas pedal by the occupant, an actuation of a switch by the occupant, and/or a voice of the occupant. On the basis of the sensed acceleration/deceleration request, a coverage range of the sensor that is used for the ACC system is changed. In particular, upon a request for a deceleration, the coverage range is increased laterally, if the occupant's request for a deceleration is sensed so that vehicles, cutting in from the side in front of the vehicle to be controlled, are detected earlier, and the system automatically adjusts itself to those vehicles. In contrast, the coverage range is decreased laterally, if the acceleration/deceleration detector senses a request for an acceleration, thus preventing an unnecessary execution of a vehicle control on the basis of the vehicles cutting in from the side.
German patent document DE 103 43 178 A1 discloses a driver assistance system with variable longitudinal guidance strategies. This system exhibits a strategy module for the variable determination of the longitudinal guidance system to be applied. In this case, there are a variety of different longitudinal guidance strategies, such as “comfort emphasized,” “normal” or “dynamic,” which are or can be stored beforehand. The driver can select one of these strategies before starting the trip and, if necessary, also during the trip. Basically the strategies differ in their different positive/negative acceleration characteristics.
German patent document DE 196 40 694 A1 describes a method and a device for controlling the driving speed of a vehicle. In this case, the limit of the speed change of the vehicle, as a function of the driver's desired dynamic characteristic of the vehicle, in particular as a function of the shift state of at least one driver-operable operator control element, is suspended or set to higher values. In this case, the acceleration and/or the deceleration dynamics of a driving speed control system are designed so as to be adjustable. Therefore, since the driver sets the acceleration and/or deceleration dynamics, he is tied into the system. Since in this case the limit values of the maximum acceleration and/or deceleration that is set by the system are changed, the effect of the intervention becomes clear only when the automatic speed control system executes an acceleration, acceleration change, deceleration and/or a deceleration change that exceeds the old limit values.
Moreover, German patent document DE 100 19 190 A1 discloses a method for the adaptive control of the separation distance and/or driving speed of a motor vehicle. In this case, the magnitude representing the setpoint acceleration is formed and/or limited at least as a function of at least one base value; and external and internal acceleration requests can be converted by way of respectively defined of base values. In particular, for comfort and safety reasons, the vehicle acceleration ought not to be changed in arbitrary jumps, but rather the jolt, which is defined as a temporal change in acceleration, is limited by limit values in the positive and negative direction. Then a new setpoint acceleration is determined by way of a minimum base value, a maximum base value, the limit values, and the past setpoint acceleration. The maximum base value is that value that must exceed at least a setpoint acceleration defined by the ACC controller, so that a positive acceleration change of the vehicle ensues. The minimum base value is that value that must fall below at least a setpoint acceleration that is defined by the ACC controller, so that a negative acceleration change of the vehicle ensues. During active control, the minimum base value and the maximum base value are formed from a current base value and the last setpoint value. During all transitions into the drive case or the active control mode, the minimum base value and the maximum base value are initialized to the current base value. During control with brake intervention, the minimum base value and the maximum base value are formed from base values, provided by a deceleration controller and/or an active brake, and the last setpoint value. When the setpoint value is below the minimum acceleration of the drive, but the brake intervention has not yet been activated, the maximum base value is formed by way of a minimum acceleration value; and the minimum base value is formed by way of a minimum acceleration value, decreased by a brake engagement hysteresis value. If the driver of the motor vehicle requests a higher engine output than the ACC system demands (driver override), the maximum base value is set as the current base value; and the minimum base value is set as a value aDrvMin that is not closely defined.
The common feature of all of these systems is that the driver is always confronted with the decision of whether he would like to let the system drive or whether he himself would like to drive. Only in an indirect manner is it possible to intervene in the system, which the intervention does not disengage—at least temporarily. For this reason, critical situations cannot be adequately avoided by decelerating or accelerating while simultaneously maintaining the active control.
Accordingly, the invention provides an improved driver assistance system for a vehicle having a controller for the control of the acceleration of the vehicle according to a setpoint acceleration value.
According to the invention, a driver assistance system for a vehicle with a controller for the control of the acceleration of the vehicle according to a setpoint acceleration is provided, which has an input coupling unit for coupling an additional acceleration that can be predefined by the driver of the vehicle.
Accordingly, the invention provides for intervention in the driver assistance system, carefully incorporated possibilities in the natural and intuitive actions and reactions of the driver. By using an input coupling unit for the input of the additional acceleration that can be predefined by the driver of the vehicle, the driver is enabled, by virtue of the superimposed control, to feed additional acceleration requirements into the speed control system. With this regulation concept, the requirements of the driver and the requirements of the system are processed to obtain a total acceleration and integrated in the control. Due to this procedure, the operating mode changes, so that the driver now drives in association with the system. As a result, the driver need not switch off the system so frequently. The driver can override the system in certain situations (through the additional acceleration demands) without switching it off. As soon as the driving situation is handled, then the driver withdraws (ends his additional demand) and the system takes over again the complete control automatically. The driver thus actively participates in the process of control and is thus “in the loop.”
Hence, according to the invention, the degree of automation, for example, the ACC function, is reduced in such a manner that the driver can modify the setpoint acceleration or the setpoint retardation (=negative setpoint acceleration) of the vehicle specified by the ACC control by use of a suitable operator control element such that with it, the driving as desired by him (desired acceleration and deceleration) that deviates that by the ACC system, which is possibly based on his assessment of the driving situation that deviates from that of the ACC system, can inform the acceleration controller provided in the ACC system without leading to an interruption of the ACC function.
An adjustment mechanism of that type for the superimposition of the driver input on a setpoint acceleration or a setpoint deceleration, deviating from that of the system input, can be present as a manually operated element with a defined null position and a continuously accessible positive and a negative adjustment range. This operating element is, preferably, arranged within the accessible reach of the driver, for example in the vicinity of the gear selection stick, in a multifunction steering wheel, in the form of a steering control arm, etc. The operating element is preferably selected in a manner consistent with the driver expectations, so that intuitive driver reactions for accelerations and retardation are enabled as far as possible, for example in case of a horizontal arrangement of the operating element, the following operating mechanisms can be suitable: forward=increase system acceleration, backward=decrease system acceleration.
Due to these values generated by the driver by way of the operating element, the setpoint acceleration generated by the system is modified so that the effect of the system is continuously weakened and the effect of the driver operation is strengthened. The characteristics of the controlling engagement of the operating element can be designed arbitrarily, with a linear, progressive, degressive, symmetrical, asymmetrical and/or with a characteristic time response, in order to fulfill the requirements related to scalability, vehicle reaction, dynamic experience, optimal driver-vehicle control loop performance, etc.
Further, this problem is solved according to invention with a method for the control of the acceleration of the vehicle according to the setpoint acceleration by using a controller, in which an integration of the additional acceleration that can be prespecified by the driver of the vehicle manually takes place.
According to the invention, preferably, an additional acceleration is superimposed on the system acceleration so as to generate the setpoint acceleration. For that, the regulator of the driver assistance system according to the invention preferably includes an acceleration controller, which receives the setpoint acceleration, whereby the input coupling unit, which generates the setpoint acceleration through superimposition of the additional acceleration on the system acceleration, is arranged upstream before the acceleration controller.
According to the invention, preferably a compensation for a disturbance variable takes place, which acts on the setpoint acceleration. For that, the acceleration controller of the driver assistance system according to the invention preferably includes a disturbance variable monitor, which acts on the setpoint acceleration.
According to the invention, the system acceleration is preferably generated by the speed controller. For that, the controller of the driver assistance system according to the invention preferably includes a speed controller, which outputs the system acceleration, whereby the input coupling unit is arranged downstream after the speed controller and the setpoint acceleration is generated through the superimposition of the additional acceleration on the system acceleration.
According to the invention, the superimposition of the additional acceleration on the system acceleration takes place preferably through addition of the additional acceleration to the system acceleration, that is, in the driver assistance system according to the invention, the input coupling unit is preferably a summing unit.
With these embodiments according to the invention, the manual superimposition of an acceleration to a system acceleration has the effect similar to an acceleration disturbance in a closed control loop. The coupling of the manually provided additional acceleration does not takes place within the disturbance variable monitor feedback, in order not to compensate the manually provided additional acceleration by the disturbance variable monitor. The speed controller and a distance controller, possibly arranged upstream before it, have preferably no such integral components that act on the respective difference variable difference, in order that the effect of the manually provided additional acceleration is not offset as a result of it.
With this arrangement of the acceleration operation according to the invention, driving situations, such as, for instance, with a near cut-in of a vehicle, can be handled without the actuation of the brakes and thus without deactivation of the assistance system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.